perf: Reduce RTC connection times (#341)

Author: kylecarbs

wsnet/dial.go

@@ -113,17 +113,16 @@ func (d *Dialer) negotiate() (err error) {
 
 	go func() {
 		defer close(errCh)
-		err := waitForDataChannelOpen(context.Background(), d.ctrl)
+		err := waitForConnectionOpen(context.Background(), d.rtc)
 		if err != nil {
 			_ = d.conn.Close()
 			errCh <- err
 			return
 		}
-		d.ctrlrw, err = d.ctrl.Detach()
-		if err != nil {
-			errCh <- err
-		}
-		_ = d.conn.Close()
+		go func() {
+			// Closing this connection took 30ms+.
+			_ = d.conn.Close()
+		}()
 	}()
 
 	for {
@@ -179,7 +178,20 @@ func (d *Dialer) Close() error {
 
 // Ping sends a ping through the control channel.
 func (d *Dialer) Ping(ctx context.Context) error {
-	_, err := d.ctrlrw.Write([]byte{'a'})
+	// Since we control the client and server we could open this
+	// data channel with `Negotiated` true to reduce traffic being
+	// sent when the RTC connection is opened.
+	err := waitForDataChannelOpen(context.Background(), d.ctrl)
+	if err != nil {
+		return err
+	}
+	if d.ctrlrw == nil {
+		d.ctrlrw, err = d.ctrl.Detach()
+		if err != nil {
+			return err
+		}
+	}
+	_, err = d.ctrlrw.Write([]byte{'a'})
 	if err != nil {
 		return fmt.Errorf("write: %w", err)
 	}

wsnet/listen.go

@@ -103,7 +103,7 @@ func (l *listener) dial(ctx context.Context) (<-chan error, error) {
 // Negotiates the handshake protocol over the connection provided.
 // This functions control-flow is important to readability,
 // so the cognitive overload linter has been disabled.
-// nolint:gocognit
+// nolint:gocognit,nestif
 func (l *listener) negotiate(conn net.Conn) {
 	var (
 		err     error
@@ -172,11 +172,17 @@ func (l *listener) negotiate(conn net.Conn) {
 				closeError(err)
 				return
 			}
+			rtc.OnConnectionStateChange(func(pcs webrtc.PeerConnectionState) {
+				if pcs == webrtc.PeerConnectionStateConnecting {
+					return
+				}
+				_ = conn.Close()
+			})
+			flushCandidates := proxyICECandidates(rtc, conn)
 			l.connClosersMut.Lock()
 			l.connClosers = append(l.connClosers, rtc)
 			l.connClosersMut.Unlock()
 			rtc.OnDataChannel(l.handle)
-			flushCandidates := proxyICECandidates(rtc, conn)
 			err = rtc.SetRemoteDescription(*msg.Offer)
 			if err != nil {
 				closeError(fmt.Errorf("apply offer: %w", err))

wsnet/rtc.go

@@ -155,6 +155,8 @@ func dialICEURL(server webrtc.ICEServer, rawURL string, options *DialICEOptions)
 // Generalizes creating a new peer connection with consistent options.
 func newPeerConnection(servers []webrtc.ICEServer) (*webrtc.PeerConnection, error) {
 	se := webrtc.SettingEngine{}
+	se.SetNetworkTypes([]webrtc.NetworkType{webrtc.NetworkTypeUDP4})
+	se.SetSrflxAcceptanceMinWait(0)
 	se.DetachDataChannels()
 	se.SetICETimeouts(time.Second*5, time.Second*5, time.Second*2)
 
@@ -165,6 +167,7 @@ func newPeerConnection(servers []webrtc.ICEServer) (*webrtc.PeerConnection, erro
 		if server.Credential != nil && len(server.URLs) == 1 {
 			url, err := ice.ParseURL(server.URLs[0])
 			if err == nil && url.Proto == ice.ProtoTypeTCP {
+				se.SetNetworkTypes([]webrtc.NetworkType{webrtc.NetworkTypeTCP4, webrtc.NetworkTypeTCP6})
 				se.SetRelayAcceptanceMinWait(0)
 			}
 		}
@@ -213,6 +216,25 @@ func proxyICECandidates(conn *webrtc.PeerConnection, w io.Writer) func() {
 	}
 }
 
+// Waits for a PeerConnection to hit the open state.
+func waitForConnectionOpen(ctx context.Context, conn *webrtc.PeerConnection) error {
+	if conn.ConnectionState() == webrtc.PeerConnectionStateConnected {
+		return nil
+	}
+	ctx, cancelFunc := context.WithTimeout(ctx, time.Second*15)
+	defer cancelFunc()
+	conn.OnConnectionStateChange(func(pcs webrtc.PeerConnectionState) {
+		if pcs == webrtc.PeerConnectionStateConnected {
+			cancelFunc()
+		}
+	})
+	<-ctx.Done()
+	if ctx.Err() == context.DeadlineExceeded {
+		return ctx.Err()
+	}
+	return nil
+}
+
 // Waits for a DataChannel to hit the open state.
 func waitForDataChannelOpen(ctx context.Context, channel *webrtc.DataChannel) error {
 	if channel.ReadyState() == webrtc.DataChannelStateOpen {